Structural Polymorphism Kinetics Promoted by Charged Oxygen Vacancies in HfO_{2}.

Defects such as oxygen vacancy are widely considered to be critical for the performance of ferroelectric HfO_{2}-based devices, and yet atomistic mechanisms underlying various exotic effects such as wake-up and fluid imprint remain elusive. Here, guided by a lattice-mode-matching criterion, we systematically study the phase transitions between different polymorphs of hafnia under the influences of neutral and positively charged oxygen vacancies using a first-principles-based variable-cell nudged elastic band technique. We find that the positively charged oxygen vacancy can promote the transition of various nonpolar phases to the polar phase kinetically, enabled by a transient high-energy tetragonal phase and extreme charge-carrier-inert ferroelectricity of the polar Pca2_{1} phase.

[Effects of patient-controlled analgesia with small dose ketamine combined with morphine and the influence thereof on plasma beta-endorphin level in patients after radical operation for esophageal carcinoma].

Objective: To evaluate the effects of patient-controlled analgesia (PCA) with small dose ketamine combined with morphine on analgesia and influence thereof on the plasma beta-endorphin (EP) level in the patients after radical operation for esophageal carcinoma.

Methods: Thirty ASAI-II patients, aged 35-65, weighing 42-75 kg, with visual analogue score>or=3, undergoing elective radical operation for esophageal carcinoma under general anesthesia received intravenous morphine 2 - 3 mg were randomly divided into 2 equal groups: group m receiving morphine 0.02 mg.